Field of the Disclosure
Embodiments disclosed herein relate to methods and apparatuses to removably cover service access ports of industrial machines. More particularly, embodiments disclosed herein relate to apparatuses and methods to removably cover service access ports of hydraulic industrial machines and pumps. More particularly still, embodiments disclosed herein relate to apparatuses and methods to retain vibration resistant service access covers within service access ports of oilfield pumps.
Description of the Related Art
Well service pumps, commonly known in the oilfield industry as “mud pumps,” are ubiquitous in oilfield drilling and exploration operations. In general, well service pumps are frequently used to supply fluids to remote destinations (e.g., deep wellbore locations) at pressures exceeding 20,000 psi (138 kPa). Most commonly, well service pumps are used to transmit drilling fluid, commonly referred to as “mud,” from a surface holding tank, through a central bore of a plurality of threaded drill pipes to a drill bit located at the bottom of the wellbore.
Once at drill bit, the pressurized mud is allowed to flow over cutting surfaces of the drill bit and “wash” the freshly-cut wellbore formation. Following exit through nozzles of the drill bit, the pressurized mud escapes up the wellbore and back toward the surface through a wellbore annulus formed between the outer diameter of the drillstring and the inner diameter of the (cased or uncased) wellbore. Because the annular area between the drillstring and the wellbore is greater than that of the central bore, the mud returns at a pressure that is reduced from its delivery pressure. Additionally, as the returning mud is used to remove drill cuttings and other entrained solids from the wellbore, it must be filtered as it is collected at the surface before it may be returned to the holding tank for a return trip downhole.
Mud pumps, as most commonly deployed in the oilfield industry, are typically constructed as multi-cylinder reciprocating pumps, although some circumferential or positive-displacement pumps have been used. Typically, oilfield mud pumps come in either the triplex (i.e., three cylinder) or the quintuplex (i.e., five cylinder) varieties, whereby each “cylinder” comprises a suction end and a discharge end. Ordinarily, a pair of one-way check-type valves are situated between the suction and discharge ends of each cylinder and are arranged such that fluid is drawn into the cylinder from the suction end through a first check valve, and then forced from the cylinder to the discharge end through a second check valve. A motor-driven plunger (i.e., piston) reciprocates within the cylinder alternating suction and discharge strokes with each complete rotation cycle of the crankshaft. Typically, the multiple cylinders of a multi-cylinder mud pump are timed such that the overall output of the pump is balanced and does not represent the overall pulsed nature that would be exhibited by a single-cylinder check valve pump.
Referring now to FIG. 1, a mud pump assembly 100 as would be commonly known in the prior art is shown. As depicted, mud pump 100 includes a power end 102 and a fluid end 104. As would be understood by those having ordinary skill, the power end 102 comprises the driving assembly including an electric motor, a transmission (e.g., gear reducer) apparatus, and a crankcase housing a crankshaft and a plurality of connecting rods. In operation, the electric motor drives the transmission which, in turn, rotates the crankshaft attached to each of the (in this example) three piston plungers that reciprocate into and out of fluid end 104 of the mud pump 100. As a result, drilling mud (or any other fluid to be pumped) is drawn into cylinders of fluid end 102 through an inlet or suction manifold 106 and is discharged (under pressure) through a discharge outlet 108. Finally, as can be seen in FIG. 1, a plurality of access ports 110, 112 are located within fluid end 104 of mud pump 100 to allow access to either the suction, discharge, or cylinder components of mud pump 100. As shown, ports 112 allow access to the discharge end of fluid end 104, while ports 110 allow access to the cylinder portions of fluid end 104. A gauge connection 114 is shown located within port 112a corresponding to the middle cylinder of discharge end of fluid end 104 of mud pump 100.
Referring now to FIG. 2 (alongside FIG. 1), a sectioned view of the fluid end 104 of pump 100 is shown. As one having ordinary skill would understand, a plunger 120, connected to a rod of power end 102 of pump 100 at threaded connection 122 reciprocates within a cylinder 124 through a dynamic hydraulic seal 126. As plunger 120 is pulled out of cylinder 124 by a rod of power end 102 (FIG. 1), suction is created in cylinder 124 and fluid is drawn into cylinder 124 through suction valve 128 from suction manifold 106. Next, as power end 102 (FIG. 1) of pump 100 thrusts piston 120 back into cylinder 124, the fluid suctioned from manifold 106 through valve 128 is discharged through discharge valve 130 and into discharge manifold 108. As described above, valves 128 and 130 are one-way check-type valves that are oriented so as to only allow fluid to flow in the direction from suction manifold 106 to cylinder 124, and then out through discharge 108. As such, during the suction stroke of plunger 120, valve 130 restricts fluid from flowing from discharge 108 to cylinder 124, and during the discharge stroke of plunger 120, valve 128 restricts fluid from flowing from cylinder 124 to suction manifold 106.
In order to service mud pump 100, a plurality of service ports 110, 112 are located throughout the main body of fluid end 104 of pump 100. As shown in FIG. 2, a service port 110 is shown allowing access to cylinder 124, plunger 120, and check valves 128 and 130. For each service access port 110, 112, mud pump assembly 100 includes a cover assembly that is used to hydraulically block and seal access ports 110, 112 so that fluid end 104 of pump 100 may maintain hydraulic integrity while in service, while still allowing easy removal of the cover assemblies in the event that a quick servicing or repair operation is necessary.
As shown in the prior art mud pump assembly 100 of FIGS. 1 and 2, the service cover assembly includes a cover 132 and a threaded retainer 134. In operation, a seal member 136 is placed about cover 132 and is used to form a hydraulic seal between a cover 132 and body of fluid end 104 to isolate cylinder 124 from the outside. Following the insertion of cover 132 into port 110, threaded retainer 134 is installed behind cover 132 and is threaded and torqued into compressive engagement with a rear or proximal end of cover 132 to counteract any pressure inside of cylinder 124 that might otherwise urge cover 132 out of port 110. A hex wrenching feature 138 is machined into the rear end of retainer 134 so that sufficient tightening torque can be applied to retainer 134 to impart a sufficient pre-load to hold cover 132 in place and to counteract hydraulic pressure within cylinder 124. Finally, a threaded bolt 140 may be used to tighten the connection between retainer 134 and cover 132 and resist any “backing up” of threaded retainer 134 away from cover 132 as a result of vibrations coming from mud pump 100 or any surrounding equipment. As would be understood by those having ordinary skill in the art, the threads of retainer 134 and bolt 140 may be machined in opposite tightening directions such that vibrations tending to loosen one of cover 132 and bolt 140 will act to tighten the other, offering further vibration loosening resistance to cover mechanism.
However, as those having ordinary skill in the art will appreciate, vibrations on reciprocating and rotating oilfield equipment are seldom consistent in magnitude or direction. Therefore, in the design shown in FIGS. 1 and 2, it is possible for there to exist a first vibration condition to loosen bolt 140 first, followed by a second vibration condition tending to loosen retainer 134. Therefore, an access cover mechanism capable of resisting various vibration conditions simultaneously is desirable.